MCU internal resources

The internal resources of the MCU I am talking about here are different from the internal structure of the MCU described in traditional MCU books. The internal resources I am talking about here refer to the things that the MCU provides us with for use as MCU users. In summary, there are three major resources:

Flash: Program storage space. Early microcontrollers used OTPROM.

RAM: data storage space.

SFR: Special Function Register.

1) Flash

In the early single-chip microcomputers, OTPROM (One Time Programmable Read-Only Memory) was mainly used to store the program of the single-chip microcomputer. The program could only be written once. If it was found to be wrong, there was no choice but to replace it and rewrite it. With the development of technology, Flash has become the program memory of most single-chip microcomputers with its advantages of repeated erasing, large capacity and low cost. For single-chip microcomputers, the greatest significance of Flash is that data will not be lost after power failure. This concept is similar to the hard disk of our computer. We save movies, documents, music and other files. After turning off the power, all the files will still exist when the computer is turned on again next time.

2) RAM

RAM is the data storage space of the microcontroller, which is used to store the data generated and needed during the program running. It is similar to the memory of the computer. In fact, the most typical analogy is our calculator. When we use the calculator to calculate addition and subtraction, some intermediate data will be saved in RAM. The data will be lost after the power is turned off, so every time we open the calculator, we start the calculation from zero. However, its advantages are, first, the read and write speed is very fast, and second, it can be written unlimited times in theory, that is, the life is unlimited, no matter how the program runs or how it is read and written, it will not break.

3) SFR

The third resource is SFR, special function register. You may not understand this concept at first, but you must remember it. The microcontroller has many functions, each of which corresponds to one or more SFRs. We realize the various functions of the microcontroller by reading and writing SFRs.

At this point, let's learn about 51 MCU. Usually, when we talk about 51 MCU, we are referring to a series of MCUs compatible with Intel MCS-51 architecture, and 51 is a popular abbreviation for it. Many semiconductor manufacturers around the world have launched countless MCUs in this series, such as Atmel's AT89C52, NXP (Philips)'s P89V51, and Hongjing Technology's STC89C52... The specific models vary greatly, but their basic principles and operations are the same, and the program development environment is also the same. Here we need to distinguish the relationship between the general term 51 and the specific MCU models.

Now that we know the three main parts of the microcontroller's internal resources, we will choose the STC89C52 microcontroller for study. STC89C52 is a 51-core microcontroller produced by Hongjing Technology. It has a standard 51 architecture and all 51 standard functions. The program download method is simple and convenient for learning. We will use it to learn microcontrollers. Its resources are as follows:

The Flash program space is 8K bytes (1K=1024, 1 byte = 8 bits);

The RAM data space is 512 bytes;

We will mention and apply SFR one by one later.